My-Weekly-ToDo-List/.planning/research/ARCHITECTURE.md

Architecture Patterns

Domain: Weekly Task Management Application Researched: January 24, 2026

Recommended Architecture

A weekly task management application with calendar integration follows a layered architecture pattern with distinct component boundaries. The architecture consists of:

1. Frontend Layer - User interface for weekly view, drag-and-drop functionality, and calendar integration
2. Backend Layer - API services for task and calendar data management
3. Data Layer - Database for storing tasks, events, and user preferences
4. Integration Layer - Services for Apple Calendar and Google Calendar synchronization

This structure enables scalability, maintainability, and supports the core requirement of displaying tasks and events in a single weekly view.

Component Boundaries

Component	Responsibility	Communicates With
Frontend	User interface rendering, drag-and-drop operations, weekly view display	Backend API, Integration Layer
Backend API	Business logic, task/event management, authentication	Database, Integration Layer
Database	Persistent storage of tasks, events, calendar integrations, user data	Backend API
Calendar Integration	Sync with Apple Calendar and Google Calendar	Backend API, External Calendar APIs

Data Flow

1. User interacts with weekly view in frontend (drag-and-drop, add/remove tasks)
2. Frontend communicates changes to Backend API via RESTful services
3. Backend API processes business logic and validates data
4. Backend accesses Database for storage/retrieval of task/event data
5. For external calendar sync, Backend API communicates with Calendar Integration Layer
6. Calendar Integration Layer manages OAuth flows and data synchronization
7. Updates are pushed back to frontend for immediate UI refresh

Patterns to Follow

Pattern 1: Layered Architecture

What: Separation of concerns into distinct layers (presentation, business logic, data) When: For scalable, maintainable codebase Example:

// Frontend layer
const WeeklyView = () => {
  // Renders weekly view with task/event cards
}

// Backend layer
const TaskService = {
  async createTask(taskData) {
    // Business logic validation
    const task = await database.saveTask(taskData);
    return task;
  }
}

Pattern 2: Observer Pattern for Real-time Updates

What: Components notify each other of changes in real-time When: For synchronous updates between frontend and backend when tasks are moved Example:

// Event emitter for task movement
const taskEmitter = new EventEmitter();
taskEmitter.on('taskMoved', (taskId, newDay) => {
  // Update UI immediately
  updateWeekView(taskId, newDay);
});

Pattern 3: Service Layer for Calendar Integration

What: Encapsulate external calendar API interactions in dedicated services When: For managing multiple calendar providers and complex sync logic Example:

class CalendarSyncService {
  async syncWithGoogle(calendarEvents) {
    // Handle Google Calendar OAuth flow
    // Update local DB with synced events
  }
  
  async syncWithApple(calendarEvents) {
    // Handle Apple Calendar integration
    // Update local DB with synced events
  }
}

Anti-Patterns to Avoid

Anti-Pattern 1: Monolithic Frontend

What: All UI logic bundled in single files without separation Why bad: Makes maintenance difficult as application grows Instead: Use component-based architecture with clear separation of concerns

Anti-Pattern 2: Direct Database Access

What: Frontend components querying database directly Why bad: Security vulnerabilities, tight coupling, scalability issues Instead: Use API layer to mediate all data access

Anti-Pattern 3: Inconsistent Calendar Sync Logic

What: Different sync approaches for different calendar providers Why bad: Leads to data inconsistency and user confusion Instead: Implement standardized sync protocols with clear error handling

Scalability Considerations

Concern	At 100 users	At 10K users	At 1M users
Task Creation/Updates	Local caching with optimistic updates	Load balancer with database connection pooling	CDN for static assets, sharded database
Calendar Integration	Single-threaded sync per user	Parallel sync workers	Distributed sync services, queue processing
Concurrent Drag-and-Drop	Immediate updates with local state	Server-synchronized updates with conflict resolution	Real-time WebSocket connections for instant updates

Sources

• General software architecture principles from Martin Fowler's writings
• Layered architecture patterns commonly used in web applications
• Task management application design patterns from industry best practices
• Component-based architecture guidelines for scalable frontend development